The present invention relates to a new method of synthesis enabling benzyl methacrylate and some of its derivatives to be obtained in a simple manner and in a high yield.
Benzyl methacrylate and its derivatives which are chlorinated or alkylated on the aromatic nucleus are methacrylic monomers which are widely employed, for example, in copolymerization with other monomers, especially acrylic, methacrylic and vinylaromatic monomers and the resultant copolymers are fabricated into various conventional products described in the literature. It is therefore important from the viewpoint of uses in copolymerization that these monomers may be obtained in a manner which is as simple and as economical as possible.
One of the methods of synthesis of benzyl methacrylates and of its most commonly employed derivatives consists of the transesterification of methyl methacrylate with benzyl alcohol or its derivatives which are chlorinated or alkylated on the aromatic nucleus. However, this reaction is made tricky by the fact that benzyl alcohol can be easily oxidized to benzaldehyde by the atmospheric oxygen needed for stabilizing the monomer under the reaction conditions.
Another method of synthesis consists in starting with benzyl chloride. Thus, Soviet Patent No. 415,345 describes the synthesis of benzyl methacrylate from benzyl chloride and methacrylic acid in an aprotic polar solvent such as dimethylformamide and in the presence of a stoichiometric quantity of a scavenger for hydrochloric acid, such as a tertiary amine, at a temperature of 20.degree. C. to 60.degree. C. When this reaction is performed at 50.degree. C. for 2.5 hours, the yield attained is 75%. Furthermore, J. Dvorak in Chem. Abstracts, 53, 2144b has described the synthesis of benzyl methacrylat from benzyl chloride and sodium methacrylate in the presence of a tertiary amine. When using 10 mol % of tributylamine, a 60% yield of benzyl methacrylate is thus obtained after 2.5 hours.